Quote from Hoi:
Understand that when you have a IB universal Account it does not matter what you trade or in what country you live....if you trade a DAX-future, you will get Euro's in your account (P&L and commission).
The same as you trade Forex, you are just MOVING currencies, between your base-currency and foreign currencies....If your base-currency is set to USD, then all other currencies are foreign. It does not matter if that is EUR or CAD.
Margin is only calculated for foreign-currencies.....Your started this thread with a question why your USD.GBP trade took 4% instead of 2%...that is because both are FOREIGN to your CAD (base)...if you want 2% then the solution is to take USD as base....if you don't want that...well then you have to accept 4% at IB (or trade FX-futures on Globex, which are better anyway).
Learn to THINK in budgets, not in what country you live.
If you want to keep as much of your account in CAD then you can, but when USD is your base it is a position in foreign-curr, so it will take 2% Margin....
Also the Interest might be something to consider. as USD interest is currently higher than CAD it is actually GOOD to have USD as your base and keep all your money it USD (until you close your account).
PS: I have one of my accounts in USD, while I live in The Netherlands (in Euro).